Protective device for jet engines



Aug. 5, 1958 v. MILLMAN PROTECTIVE DEVICE FOR JET ENGINES Filed April19, less 2 Sheets-Sheet 1 FIG. 2

INVENTOR. VICTOR M/LLMA/V A T TOR/VE' Y 1958 v. MILLMAN 2,846,023

, PROTECTIVE DEVICE FOR JET ENGINES 2 Sheets-Sheet 2 Filed April 19,1956 24 FIG. 4

28 INVENTOR.

VICTOR MlLLMA/V 21 e Bgxpwbcu1 ATTORNEY PnoTEcrrvE DEVICE FOR JETENGINES Victor Millman, San Diego, Caliii, assignor to General DynamicsCorporation, San Diego, Calif., a corporation of Delaware ApplicationApril 19, 1956, Serial No. 579,243 7 Claims. (Cl. 183-51) The presentinvention relates to protective screen devices and more particularly, animproved form of screen device for use in connection with jet enginesfor entrapment of foreign matter at the air inlet of an engine.

Prior to actual flight of an airplane, certain adjustments and checksmust be made by ground crew personnel which necessitates operating theengines while the airplane remains on the ground. Suction created by ajet engine is of such force as to pick up debris of foreign material inthe immediate vicinity of the engine air scoop and unless restrainedsuch debris is carried into the internal mechanism of the engine. Due tothe extreme high velocity of the engine, small solid particles on theground such as pebbles, stones, nuts, bolts and the like, sucked intothe engine have caused either considerable damage to, or completedestruction of, the engine. In an attempt to avoid damage to an enginefrom foreign matter entering the air inlet, ground testing areas must beswept at frequent intervals in an attempt to rid the area of materialwhich might prove destructive. Even though the ground is swept certainobjects may be missed or may be dropped inadvertently in the area aftera sweeping.

To prevent foreign matter entering the air inlet of the engineprotective screens have been employed. However in the use of aprotective screen with the air scoop of the engine, it has been foundthat a screen, to serve effectively the desired purpose, must satisfycertain conditions. The screen must be so constructed that it will notrestrict or impede the volumetric air flow to a degree which wouldresult in overheating and subsequent damaging of the engine. Also, thescreen must have sufficient strength to resist inward collapse. Afurther consideration preferably requires the major portion of theintake air to be drawn from above the engine rather than from the frontand sides. The screen should be compact, light, and, since it isrequired only while the engine is being ground tested, readilydetachable from the engine air scoop before flight of the airplane.

It is, therefore, the principal object of this invention to provide animproved form of screen having the desirable characteristics, as aboveenumerated, and which serves etfectively to filter deleterious foreignmaterial from the air entering the air inlet of a jet engine.

Another object of this invention is to provide a protective screen ofimproved construction, being in the form of a cage with a trap elementincluded therewithin which acts to arrest and collect foreign particlesirom the air entering the engine.

Another object of this invention is to provide a protective screen ofthe type above embodying quick dis connect means to permit readydetachment of the screen from the engine.

Another object of this invention is to provide a proteetive screenfilter device for a jet engine which is simple and durable, economicalto manufacture, and efficient in operation.

Other objects and features of the present invention will States Patent 92,846,923- Patented Aug. 5, 1958 be readily apparent to those skilled inthe art from the following specification and appended drawings whereinis illustrated a preferred form of the invention, and in which:

Figure 1 is a perspective view of a screen device embodying the presentinvention and shown in operative position on a typical jet airplane.

Figure 2 is an enlarged plan view of the screen shown in Figure 1 with aportion cut away to facilitate illustration.

Figure 3 is a side elevational view with a portion cut away to show thedebris trap construction, and

Figure 4 is an end view of the present screen device.

Referring now to the drawings, a protective screen or filtering deviceconstructed in accordance with the present invention is indicatedtherein in its entirety by the numeral 1i), and, in Figure l, is shownoperatively positioned upon an air inlet scoop 11 of a typical jetpowered airplane 12.

Screen device 10 involves a body structure defining a chamber which bodystructure is of generally box-like shape, having a substantiallysegmental outline in side elevation, and which forms, in effect a cage.

Screen device 10 embodies a framework 13 suitably formed into thedesired configuration of device 10 and made of a plurality of sectionsor lengths 14, of angle iron, or of any other suitable metal, thevarious sections being appropriately connected at their ends to one another, as by welding, to effect a rigid structure. Afiixed to framework13 are a top member or panel 15, a pair of side members 16 of generallysegmental outline, and a member 17, of arcuate form, which extends fromtop member 15 to form an end and the bottom of the cage; top member 15,as shown, may slope downwardly from its joinder at the upper edge ofwall member 17 to its joinder with the rear end of screen device 10.Member 17 and side members 16 are formed of two layers 18 and 19 ofscreen mesh, the outer layer 18 being of relatively fine mesh havingapproximately one-sixteenth inch square openings, and the inner orbacking layer 19 being of coarser mesh having approximately onehalfsquare openings. Inner layer 19 serves to reinforce fine mesh layer 18and adds strength and rigidity to the structure. The outer and innerscreen layers 18 and 19 which comprise side members 16 and arcuatemember 17 are suitably aflixed, as by welding, to tensioning frames 21conveniently formed of flat strips of metal arranged in the desiredoutline for members 16 and 17.

Top members 15 preferably is formed of a coarse screen 22, havingapproximately one-half inch square openings, which is carried by atensioning frame 23 made of flat metallic strips.

Arcuate end and bottom member 17 and side members 16 are atfixed toframework 13 of device 10 as by welding, or in any other well-knownmanner. For convenience, top member 15 is removably secured to framework13 by suitable fasteners such as screws, in order to permit ready accessto within device 10 for cleaning purposes.

The rearward end 24 of screen device 141 confronts the opening of theair inlet scoop 11 and has an opening formed therein which conforms inoutline to the outline of the scoop opening. Figure 4 illustrates theconfiguration of a typical opening 25 in end 24 which it is to beassumed is the same as the outline of the opening of the air inlet scoopwith which the present screen device It is to be employed. Inconstructing opening 25 a plurality of appropriately shaped sections 26of metallic tubing, or angle iron, is suitably connected together, as bywelding, into a frame 2'7 of the required configuration. This frame 27is conveniently afiixed to framework 13 in end 24 by tubular elements orbraces 28 having Welded connections to the frame 27 and framework 13.Included at end 24 are two layers 18 and 19 of screen mesh identical tothe layers 18 and 19 of side members 16 and arcuate member 17, layer 18being of relatively fine mesh and layer 19 being coarser and serving toreinforce the first layer. It is understood, of course, that layers 18and 19 are applied in surrounding relation to opening 25 and offer noobstruction to such opening.

Located at end 24 are a plurality of clip members 31 formed of metalhaving some resiliency such as spring steel which are rigidly secured toframe 27 defining opening 25 by nut and bolt assemblies 32, or, ifdesired, these clip members may be riveted in place. Clip members 31project rearwardly from end 24 and are adapted to fit with resilientpressure about the edge contour of air inlet scoop 11 to position screendevice properly relative to the scoop. To maintain device 10 on scoop 11against inadvertent dislodgment the uppermost of the clips 31 may besecured to the scoop by a temporary fastener such as a screw.

Within the chamber of cage-like construction of device 10 formed by thescreen-covered framework 13 is positioned a generally rectangular trapor barrier member 33. Trap 33 is located upon the bottom of device 10near the rearward wall 24 and extends upwardly from the bottom and isforwardly inclined. Trap 33 extends transversely across the bottom ofdevice 10 from side member to side member thereof and is formed of aforward layer 34 of relatively fine mesh screen, similar to outer screenlayer 18 above described, backed by a coarse screen layer 35, similar toinner layer 19 hereinbefore mentioned. These screen layers are suitablysecured to a frame 36 formed by side angle members 37 rigidly connectedin spaced apart relation to framework 13 and a transverseinterconnecting angle member 33 afiixed to the upper ends of sidemembers 37. Brace members 41 interconnected between framework 13 andframe 36 may be provided for support of frame 36.

As has been described, arcuate member 17 and side members 16, in theirconstruction, include two screen layers 18 and 19, with the first beingof finer mesh than the second, while top member includes but one screenlayer which is of coarse mesh. By reason of this screen arrangement, itis apparent that air will more readily enter through top member 15 sinceless obstruction is afforded to the air. Thus, the major volume of airwhich is supplied to air inlet scoop 11 enters device 10 by way of topmember 15. It is necessary that top member 15 be more open than thesides or bottom of device 10 to assure that a sufficient volume of airis provided to the engine. Obviously, if not enough air were providedthe engine would overheat and be damaged.

Screen device 10 is made of suflicient height that the more open topmember 15 will be located above the uppermost edge of the air inletscoop 11 so that the major volume of inlet air supplied to the scoop istaken into device 10 from above the scoop and is directed downwardly byarcuate wall member 17 to the scoop. The purpose of arcuate wall member17 will be hereinafter more fully described.

In operation, screen device 10 is positioned upon the air inlet scoop ofthe jet engine to be serviced with its opening aligned with the openingof the scoop. With the jet engine running, some inlet air is drawnthrough all the screened surfaces of device 10 but the major portion issupplied from above through top member 15. The arcuate form of wallmember 17 causes the air entering from top member 15 to move in suchfashion that the solid objects which may have been carried in are causedto gravitate to the bottom and to pass along the arcuate Wall memberuntil arrested by trap 33; in effect, device 10 acts as a centrifuge.Trap 33 is of suffieient height that it will effectively bar passage offoreign material to the air inlet scoop, but will not offer anyappreciable barrier or disturbance to the flow of air to the scoop. Theetfective height of trap 33 can be readily determined by test methodsemploying suction devices or the like.

By enclosing the sides and bottom of device 10 with a fine mesh screen,as described, it has been found that objects of a size harmful to theengine will be effectively filtered from such inlet air as entersthrough the fine mesh screen. Also by causing the major volume of theair used by the engine to enter from the top of device 10 it renders itmore difiicult for objects of harmful size to be carried into device 10,and should harmful objects e carried up, over and pass through thescreen of top member 15 into device 10 the arcuate wall member 17 willdirect these objects against trap 33 to be arrested thereby. As statedabove, the present screen device 10 is not intended to be a permanentattachment to the jet engine. After the necessary tests and checks havebeen made screen device 10 is removed by withdrawing the attaching screwjust prior to take-off.

It is understood that the present invention is not to be limited toscreen mesh having openings of the size described, and that the screenswhich have been described are to be considered only as examples.

From the foregoing it will be seen that there has been provided a screendevice which effectively protects the jet engine from foreign harmfulobjects while permitting the entrance of sufficient volume of air forproper operation of the engine. The present invention also serves as asafety device in another respect in that, by reason of its sturdyconstruction, it offers protection to personnel who working in the areaof the jet engine might accidentally be drawn by the air toward theengine.

While a certain preferred embodiment of the invention has beenspecifically disclosed, it is understood that the invention is notlimited thereto as many variations will be readily apparent to thoseskilled in the art and the invention is to be given its broadestpossible interpretation within the terms of the following claims:

What I claim is:

l. A protective device for use with the air inlet of a jet engine forfiltering foreign material from air entering said air inlet comprising abody structure defining a chamber and having its wall members formed ofscreen for the passage of air, including among its wall members a topwall member and a rear wall member, the screen of said top wall memberbeing of coarser mesh than the screen afforded the other wall membersfor the more ready passage of air therethrough into the body structure,said rear wall member having an opening therein adapted for alignmentwith the opening of said air inlet, and one of said other wall membersextending downwardly and rearwardly from said top wall member to saidrear wall member and being of generally arcuate configuration.

2. A protective device for use with an air inlet of a jet engine forfiltering foreign material from the air entering said air inlet, saiddevice comprising a closed wall screened cage, said walls of said cageincluding a top wall covered with screen of coarser mesh than the otherscreened walls for the more ready passage of air into said cage, anotherof said walls having an opening therein adapted to confront the openingof said air inlet, and screened trap means within said cage arranged topartially project into the intake air stream for arresting andcollecting foreign particles from the air passing through said cage.

3. A protective device for use with the air inlet of a jet engine forfiltering foreign material from air entering said air inlet comprising abody structure defining a chamber and having its wall members formed ofscreen for the passage of air, the screen of at least one of said wallmembers being of coarser mesh than the screen afforded the other wallmembers for the more ready passage of air therethrough into saidchamber, said lastmentioned wall member being arranged to be positionedabove the opening to said air inlet, one of said wall members having anopening therein adapted for alignment with the opening of said airinlet, and screened trap means within said chamber supported to projectpartially into the intake air stream for arresting and collectingforeign particles from the air passing through said chamber.

4. A protective device for use with the air inlet of a jet engine forfiltering foreign material from air entering said air inlet comprising abody structure defining a chamber and having its wall members formed ofscreen for the passage of air, including among its wall members a topwall member and a rear wall member, the screen of said top wall memberbeing of coarser mesh than the screen afiorded the other wall membersfor the more ready passage of air therethrough into said chamber, saidrear wall member having an opening therein adapted for alignment withthe opening of said air inlet, one of said other wall members extendingdownwardly and rearwardly from said top wall member to said rear wallmember and being of generally arcuate configuration, and screened trapmeans within said chamber supported to project partially into the intakeair stream for arresting and collecting foreign particles from the airpassing through said chamber.

5. A protective device for use with the air inlet of a jet engine forfiltering foreign material from air entering said air inlet comprising abody structure defining a chamber and having its wall members formed ofscreen for the passage of air, including among its wall members a topwall member arranged to be positioned above the opening to said airinlet and a rear wall member, the screen of said top wall member beingof coarser mesh than the screen afforded the other wall members for themore ready passage of air therethrough into said chamber, said rear wallmember having an opening therein adapted to be positioned at the openingof said air inlet, one of said other wall members extending downwardlyand rearwardly from said top wall member to said rear wall member andbeing of generally arcuate configuration, and a barrier member disposedwithin said chamber of said body structure, projecting partially intothe intake air stream and extending transversely across saidlast-mentioned wall member for arresting and collecting foreignparticles from the air passing through said chamber, said barrier membercomprising screening and bracing means for holding said screening inposition.

6. A protective device for use with an air inlet of a jet engine forfiltering foreign material from the air entering said air inlet, saiddevice comprising a closed wall screened cage, the top wall of said cagearranged to be positioned above the opening to said air inlet and beingcovered with screen of coarser mesh than the other screened walls forthe more ready passage of air into said cage, the rear wall of said cagehaving an opening therein adapted to confront the opening of said airinlet, and trap means disposed on the bottom wall of said cage andadjacent the rear wall thereof and projecting partially into the intakeair stream for arresting and collecting foreign particles from the airpassing through said cage, said trap means comprising screen meansextending transversely across said bottom wall, and bracing means forholding said screen means in position.

7. A protective device for use with the air inlet of a jet engine forfiltering foreign material from air entering said air inlet comprising abody structure defining a chamber and having its wall members formed ofscreen for the passage of air, including among its wall members a topwall member arranged to be positioned above the opening to said airinlet and a rear wall member, the screen of said top wall member beingof coarser mesh than the screen afforded the other wall members for themore ready passage of air therethrough into said chamber, said rear wallmember having an opening therein adapted for alignment with the openingof said air inlet, one of said other wall members extending downwardlyand rearwardly from said top wall member to said rear wall member andbeing of generally arcuate configuration, trap means within said chamberfor arresting and collecting foreign particles from the air enteringsaid chamber, said trap means comprising a screen positioned adjacentsaid rear wall, transversely across said wall of arcuate configurationand angularly inclined to said rear wall and projecting partially intothe inlet air stream.

References Cited in the file of this patent UNITED STATES PATENTS1,261,554 Knauff Apr. 2, 1918 1,619,954 Olmstead et a1. Mar. 8, 19272,399,186 Hunter Apr. 30, 1946 2,500,268 Adams Mar. 14, 1950 2,660,317Mork et al. Nov. 24, 1953 FOREIGN PATENTS 59,292 Denmark Dec. 15, 1941124,101 Australia Apr. 21, 1947

